Metal plate dimpling machine



L. c. HUCK 2,431,935

METAL PLATE DIMPLING MACHINE Filed Aug. 1940 4 Sheeta-She; 1

Dec, 2, 1947.

Q\ EW \mwhkwmv EQ \km mmm INVENTOR A @1115 C. flue r P 4, 1947- L. c. HUCK METAL PLATE DIMPLING MACHINE Filed Aug. 12, 1940 4 Sheets-Sheet 3 Dec 2, 1947. L. c. HUCK METAL PLATE DIMPLING MACHINE 4 Sheets-Sheet 4 Filed Aug. 12, 1940 jozzz ls C flzxcV? Patented Dec. 2, 1947 2,431,935 METAL PLATE DIMPI-JING MACHINE Louis C. Huck, Grosse Pointe, Mich., assignor, by mesne assignments, to Huck Manufacturing Company, Detroit, Mich., a corporation of Michigan Application August 12, 1940, Serial No. 352,204

26 Claims. 1

The invention relates generally to riveting and it has particular relation to dimple riveting and the formation of dimples in metal sheets to be riveted together.

In certain respects the present invention is related to that embodied in my copending application Serial No. 327,138, filed April 1, 1940, now Patent No. 2,292,446, wherein a simplified form of dimpling apparatus is shown along with a disclosure of methods of dimple riveting. As discussed in that application for patent, especially in conjunction with aircraft, it is extremely desirable in the riveting of the metal skin or cover, to employ rivets having heads flush with the surface of the cover in order to eliminate projections on surfaces exposed to air flow. It is a general practice in such cases where the metal cover is too thin to allow counter sinking, to dimple the metal around each rivet hole so as to provide a recess for the rivet head, Dimpling of the metal is particularly advantageous, in that it increases the shear strength of the riveted joint, since the contacting dimpled portions of the overlapping metal sheets provide a means, in addition to the rivet, for carrying the shear load.

One known method for dimpling overlapping sheets which are to be riveted consists in assembling the sheets, drilling a number of rivet holes, then disassembling the sheets and dimpling each sheet separately. This method has several disadvantages and an important disadvantage is that the process is expensive due to the amount of handling required. Another disadvantage is that the sheets may vary in thickness, especially in the case of aeroplane wing covers where the thickness of the metal is progressively decreased towards the tip of the wing and in this case dimpling of one sheet will effect a certain amount of creepin or growing of the metal while dimpling of another sheet of a difierent thickness will effect a different amount of growing or creeping of the metal. This diiierence in creeping or growing of the metal may also occur even when the metal sheets are of the same thickness as the angle of the bottom sheet dimple is usually somewhat different from the angle of the top sheet dimple due to the fact that as the metal is deformed, its thickness decreases. Difference in creeping or growing may also occur when the metal sheets have different degrees of hardness. It follows, therefore, that the dimple spacings in the two sheets will not be identical, due to the growing or creeping of the metal differently in the two sheets and when the sheets are thereafter riveted, the misfitting will tend to cause waves in the sheet which represent the excess lengths between dimples of the sheet that has crept or grown the most. Furthermore, considerable difficulty is encountered in having the dimple in one sheet fit the corresponding dimple in another sheet owing to the fact that the angles of the dimples in the two sheets'are usually not the same and the difierence moreover varies with the thickness of the sheet. Under these circumstances, any attempt to provide accurate fits between the dimples necessarily requires a large number of tools adapted, respectively, to be applicable to diilerent conditions.

In another method of dimple riveting, the rivet itself is used in the formation of the dimple after the rivet hole is drilled through the sheets. In a case of this kind, backing up tools are required at the inner side of the sheets in addition to squeezing or hammering means on the outer side of the sheets, and since the dimples are formed during a hammering or squeezing operation, it is not ascertainable whether or not the dimples are properly formed. Aside from this, a major disadvantage of the hammering process isthat a pressure pad for counteracting the bending of the sheets during dimpling cant be used, at least practically, and, therefore, simultaneous riveting and dimpling by hammering the rivet would leave a bend in the sheets.

Also, a major disadvantage of the squeezing process is that squeezing apparatus usually involves a yoke which would not be practical in many places because of inaccessibility. Moreover, the yoke arms would have to be quite long in some instances and correspondingly heavier and stronger whereas in many other instances a small yoke would be required. In fact, at different points of riveting, yokes of difierent length would be necessary and thus a number of riveting apparatus would be required.

According to another method, both sheets may be dimpled simultaneously in place by a punch on the one side and a die on the other, respectively, mounted on the arms of a press, but ordinarily this method is not very practical due to inaccessibility to both sides of the sheet, to practical limits to the length of the arms of the press, and to the different length yokes required, as stated previously. Use of hammer equipment for forming the dimples according to this method, also would not be practical due to the inability to Else a pressure pad, as also mentioned, heretoore.

Additional to the foregoing, one practice heretofore has been to employ a die member having a conically sided cavity for the metal to be 3 dimpled into and a conically sided tool for pressing the metal into the die and then to employ powerful forces or pressures which caused the sheet metal to be squeezed between the side walls of the die and tool until the dimple angles conformed to the angles of the tool and die. This type of operation is complicated by thefact that the metal naturally thins out towards the deeper part of the dimple and the angle of the dimple at the die side naturally tends to become different I from that at the tool side. Furthermore, this difference between angles varies with differences in thickness of sheets and, as a result,= manydifferent die and tool combinations .arerequired and the amount of squeezing varies considerably with the variations in thickness.

A further factor involved in'this prior practice and which limited the die angle or rather dimple depth at the die side of the sheets was the danger of cracking or splitting of the metal. Thus, due

-to limitations in the dieangle, it usually was necessaryto squeezethe metal even more in order to obtain the desired dimple angle at-the tool side. One object of the invention is to provide a dimpling apparatussuch as mentioned which may be operated from one side of the assembled sheets --withut'requiring more than the location of a die at-the other side of the sheets.

Another object of the invention is to provide an aefiicienig srnall, and easily m-aneuverable dimpling apparatus, .which is operated by fluid pressure.

Another-object of the-invention is to provide dimplingapparatussuch as mentioned heretofore,

which includes means forcentering and guiding amandrelinto the-end of a dimpling tool forming part of the apparatus.

Anotherobjectof the invention is-to provide a *mandrelcenteringand guiding device such as last ment-ionedwhich automatically is retracted to an -out of the way position during the dimpling operationso that it-will not interfere with movement :of the tool into-engagement with thelsheet metal.

Another object-of the invention is to provide improved means for .modifying the tendenc of .i the sheets tobend during the dimpling-operation .soithat bending will be avoided or controlled in a desirable manner.

.Another 'objectpfzthe invention is to provide an improvedidimpling apparatus having means for .counteracting this tendency 'of the sheets to bend -;during the bendingoperation, wherein the action .of'. this counteracting meansmay bevaried by adjustments. provided for this purpose.

. sAn'other object of the invention is to provide improved dimpling apparatus wherein the means .-.for.countera'cting zthe tendency of the sheets to bendduring the dimplingeoperation in-cludesa separate pressure controlled means for applying pressure ;to the .sheets around the. dimpling area.

.*.Another object of the invention is toprovide an dimpling operation, so. that. the mandrel-orpin may be easilyreleased and again inserted.

: Another obj ect. .of the. invention is toprovide an improved method of dimplingmetal sheets which will require minimum forces a while: still allowing a suitable dimpleto be formed without breaking or cracking of the dimpled metal.

Another; object of theainvention is toprovide anii-mproved mechanism 'fori dimpling meta l'sheets which will enable forming the dimple withmini mum forces and which will automatically govern the formation of the dimple by controlling the amount of force applied.

Another obj ect'of the invention is to provide an improved mechanism for dimpling metal sheets wherein the dimpling operation will automatically be, governed by stop means limiting the relative movement of the dimpling members.

Other objects of the invention will become apparent from the following description, from the drawings forming a part of the specification, and

from the claims hereinafter set forth.

For .a-better understanding of the invention,

reference'maybe had to the drawings, wherein:

. tially along the line 3-3 of Fig. 2;

Fig. 41s. a fragmentary view on the order of Fig. 1, illustrating the relation of. parts approximately at the end ofthe dimpling operation;

Fig. 5. is a cross-sectional view of dimpling apparatus in general on the order of that shown by Fig. 1, as constructed according to another form of the invention;

Fig; 6 is an enlarged detail view, in cross-section, illustrating the relation of parts. of the second apparatus. at the beginning of the dimpling operation;

' Fig. 7. is a view showing approximately the relation of the parts atthe end of the dimpling operation;

Fig. 8 is a view on the order of Fig. 1, showing another form 'ofthe invention;

r Figs. 9, 10, and 11 are detail views illustrating stepsin the operation of the mechanism shown by Fig. 8.

Referring to Fig. l, the dimpling mechanism or gun as'shown comprises a cylinder I0 having a handle ll secured thereto by suitable means not shown, so that the gun maybe manually held and manipulated. The cylinder II] has an inner cylindrical wall l2 slidably receiving a piston l3 having suitable sealing rings [4 for preventing a leakage of fluid between the 'wall and piston. At its right hand end; the cylinder is closed by an integral wall portion, excepting for a fiuid passage l5, and this passage'leads to an annular passage I! at the junction 0f -the handle and cylinder ,andin turn' the annular passage l'l communicates with a passage 18 extending through the handle for connection with a'fluid conducting line l9.

-At its left end the cylinder-IE) is enlarged thereby forming a shoulder 22 and within the enlarge- 2 ment a bushing 23 is threaded as indicated at. 24.

An annular end member 25 has a cylindrical portion 26 slidably receiving a piston rod 21 projecting from the piston l3 and a recess'28 having packing rings ZQengaging the rod and this memberis-held in place atthe. left of the cylinderby a collar 30 thereon-disposed between the end of the bushing 23 nd the shoulder 22, A gasket 3| is'located between theshoulder and collarZZv to prevent leakage of-fluid at this point.

The extreme right end of the member 25 has an annular relief 35 which communicates with a fluid passage 31 extendinglaterally through the wall of cylinder l0 and communicatin with a passage 38 leading to the handle I l "The passage 38 also extends-through a projection 4| on 'the cylinder l0 disposed in a similar opening 42 in the handle and from this point the passage is connected with a passage 43 leading to an outlet 44. Sealing gaskets 45 and 46 disposed at the junction of the casing and handle portions prevent leakage of fluid.

The piston rod 21, at its left end, terminates in a threaded portion 50 and on this threaded portion a jaw holder 5! is threaded and is retained in place by means of a lock nut 52. The left end of the jaw holder is provided with a plurality of circumferentially arranged sockets 53, which converge toward the left end of the jaw holder and which respectively receive similarly shaped jaws 54. The sockets and surfaces of the jaws may represent conical forms, or, in other words, the surface of each socket and the outer surface of each jaw may form a section of a conical surface, with the surfaces having substantially full surface contact when the jaws are in clamping positions. Grooves 56 in the inner faces of the jaws are adapted to engage a grooved mandrel to be mentioned presently, and when the end of the mandrel is between the jaws, movement of the jaw holder to the right will cause the jaw to grip the mandrel.

The jaws are urged towards the left end of the jaw holder by means of a jaw follower 51 mounted on a reduced end portion 53 of a plunger 59 that is slidably mounted in a bore 63 in the left end of the piston rod. A spring 6| in such bore urges the plunger 59 and jaw follower 5! to the left and hence th jaws to the left end of the jaw holder. It may be observed that the right ends of the jaws have angled or tapered faces 64 and that the left end of the follower 51 is similarly tapered as indicated at 65, and this relation of surfaces is provided in order to effect expansion of the jaws when forced to the right relatively to the jaw holder.

The bushing 23 has an outer cylindrical portion 61 threaded as indicated at 63 and upon which a barrel 63 is threaded, and the latter at its left end has an inwardly extending end wall terminating in a threaded aperture H adjacent the end of the jaw holder until a head 13 thereon engages the wall in of the barrel and the inner end of the tool is shaped to fit the left end of the jaws so as to provide an abutment which serves to force the jaws rearwardly when the jaw holder and piston move to the left. In other Words, just before the piston reaches its left limited position, the jaws strike the end of the tool 12 and are moved to the right relative to the jaw holder 5| and also radially outwardly into releasing position due to the relation of the surfaces 64 and 65 on the jaws and follower 51. Hence, the jaws move outwardly in their sockets to releasing positions and this movement is such that the mandrel mentioned previously may be freely removed axially from the jaws. It may be observed here that the tool 12 has an axial bore 15 leading to the jaws so that the mandrel may be inserted axially through the tool and into position between the jaws,

For dimpling sheets of metal indicated at T! and 18 disposed in overlapping relation, a die 19 is employed which has a recess 80 into which the metal is forced during the dimpling operation and a rounded edge 8! adapted to engage the sheet metal around the dimpling area for supporting the metal. This die is centrally apertured as indicated at 82 and the mandrel previously mentioned and indicated at 84 extends through this opening. The mandrel may have a press fit in A metal dimpling tool 12 is threaded into the threaded aperture H the opening 82 so that it will not be easily removable and has a head portion 83 for preventing pulling of the mandrel through the die during the dimpling operation. It may be noted that the die outwardly of the recess has its face next to the sheet metal 11 relieved as indicated at 85 and the purpose of this is to provide a space for the sheet metal to be axially pressed to the left around the dimpling area in counteracting or modifying bending caused by the dimpling operation. The mandrel 84 has a grooved or ribbed end 86 adapted to fit between the rooved jaws 54 in order to positively lock the jaws and mandrel together during the dimpling operation. For forcing the sheet metalinto the die recess 80, the tool 12 has a frusto conical end 81, which, when moved against the sheet, dimples the sheets into the die recess 80.

' It is to be observed that the die recess 80 has a flat bottom 88 and a cylindrical side wall 89 and that the edge of the sheet metal is flattened against the bottom 88 during the dimpling operation while the metal between the shoulder 8| and the flattened edge is unsupported. Thisflattened edge is indicated at 98 and during its formation the metal is upset along the mandrel as indicated at 99. Flattening of the metal edge prevents splitting or cracking and thereby allows the dimpie to be formed without danger of splitting. At the same time, by leaving the metal unsupported between the edge 98 and shoulder 8|, it is easier to form the dimple and, therefore, a smaller force may be used and this is of considerable importance since smaller pressures may be used that will not endanger breaking of the mandrel 84. It may be observed that the dimple portions tend to extrude or shift towards the die along wall 89 of the latter a slight amount as indicated at it due principally to the fact that the diameter of the wall 89 is less than the diameter of the tool i2 plus the doubled thickness of the sheets 11 and 18.

During dimpling of sheets such as mentioned, bending of the latter around the dimpling area tends to occur, and if not counteracted or modifled the sheets finally will become bowed or arcuate and this may be undesirable. To offset or modify this tendency of the sheets to bend, means are provided which will be described presently for exerting a force against the sheets during the dimpling operation and this force tends to bend the sheets over the rounded edge 8| of the die and towards the relief 85 in the die face. It may be desirable when the dimpling operation is effected to have the sheets remain flat, but again it may be desirable to variably control the amount of bending of the sheets over the edge of the die so that finally the sheets will have a desired contour. It would be even feasible to so vary the force applied to the sheets to bend them that the sheets as finally dimpled would have a bent contour opposite to that which would have been obtained through the dimpling operation alone. Therefore, it should be understood that the contour of the sheets may be varied simply by varying the pressure applied to the sheets to bend them.

It may be mentioned now that the frusto-conical end of the tool 12 presents a problem of mandrel insertion into the bore i5, because the opening for inserting the mandrel is approximately the same size as the mandrel and there is nothing on the tool end to guide the mandrel into the opening. Where dimples must be formed rapidly, some delay might be incurred in repeatf7 -'ed1y;insertingar'mandreli into thezendiofsthe tool rwithout guiding: means sand :the: construction: to be described solves this problem.

i Again directing attention-:toiFig. 1, :it will: be

4observedithatiinnereand touter. sleevesia and iii aremounted'on the barrel '69 and thesesleev'es are threadedlyz'connected at 92, sothatthe sleeves may becmoved axially. in a'relative sense by, turningxone with respect :to thecother. sTheisleeve :00 is s maintained "on Ethe -barrel ':by. :circumf.eren-.-

A tially separated pins 393.;1on the: barrel which" are :sslidably; arranged 'in'..islots"' 594 in the wall' of 1 the innerzsleevei'withzthe slots having 1 closed ends naso that'athe:rsleevesesil 'cannotzzn-ormallwbe removed. 'The two assembledsleeves are normally,

.-9i;'n:ormallywillprevent anyone from acoidentalhiya-having aifingercaughtbetWeenthe two shouluders' during-operation of the mechanism and also -=will prevent externar obj ects 50f other character .from becoming disposed in the space betweenthe ItWO S'hOUICIEIS.

Theileft end ofathe sleeve? 90 has; a relatively thick end wall I 05which. is apertured at its :center .sasrin'dicated ;-at- 4061 for" allowing passage of :the -:.to'ol'-'l2rthrough-the wall. Now for providinga rme'ans-af-or facilitating-the "insertion of the. end f-zoffthenmandrel into'the frustoconical end of the 11001112, radially disposed guide members are provided in the end wall I05 and these members have pin portions 40'! slidably: mounted inradialjopenuin'gsrl'08iinsuch-wall. r Springs -I09 in the open-, tings-J08turgethe members inwardly and the outer ends of the springs are retainedin the eopenings'by plugs "I I0 suitably secured in the .outer:end:of the latter. Theinner endsiof the spins IelSbarry-eentering or guiding'portions Ill, .respectively; and these centering portions, when brought.togetherz-asashown'in Figs. 1, 2, and 3, jointly forma 'frusto conical cavity at the right i side-whichfits-the frusto coni'cal' end ofzthe tool 12,-and at'theleit side,- a frusto conical cavity 'l I2 for guidingthepin 84.111170 thebore of tool 2:12. .It. is to be-observed that the portions LII a-zare disposed in .an annular 'ch'anneltshape'recess -H3Fand that they are guided radiallyby the walls otthe-recess. ".tering devicesare formed at their center .to .prov-ide anaopening-wl1ichwill allow the end" of 1-. the mandrel to'be pushed-therethrough.

'With the sleeve 90 moved to its extremerleft .-.-position: as, governed by. the tslots-94.and 9.3, it will be apparentthat the spring pressed guiding deviceswilrbezurged to the positions shown in Fig. 1, so' that -they-"willform1 a centering and guiding cavitywhich renders it easy to insertthe send oflthe'mandrel. On the-otherhand it-will =bewapparent that the: sleeve 90 'can be 'moved to the right easily and against theractionof :the spring .fiiandthe plunger springs 'l09'and .-that during'this operation the guiding devices will be moved outwardly by thetool 12, thereby allowi-ng-the latter to pass'rthrough .-.the end-"wall 1| 05 wofithe sleeve.

.T E'or. applying pressure toathe sheets in' order ..to..modi fy;the bending. tendency, a rubberr bush- Ling. .11! 5 sismountdaon the end. face-of the 'wall It maybe noted also thatthevcenvi 4-05 and this bushing-maybe retained in place ."by'an overhanging flange -I I6 although it may be "desirable to bond the bushing to the end 'iace 'of the wall. This rubber sleeve-is adaptedto-engage the sheet 78 and resilientlyto applypressure thereto during the dimpling operation. At-

wtention is directed-to the fact thatanang'ular -ring I20 confines the inner corner edge ofthe bushing at its outer end and this washer is pro- 'vided-mainly to prevent the rubber from being deformed inwardly into a position where it would becaught by the tool moving into the die: during 't-he'dimpli-ngoperation. I In other'words, it confines the =corner -at this-point andv governs the fl w-"of rubber and at-the same time a radial -leg'of the washer provides a metal face contact .witn t-hesheet immediately adjacent the dimpling area and this may be found desirableiin order to-insurerflatness of the sheet immediately ad- --jacent the edge of the dimpling area.

It hasbeenstated that the shoulder J00 on I the barrel 69 -isadapted to-engage the shoulder 01-zonthe sleeve 0|, andthatthis engagement will occur after a'predetermi-ned relative axial movement of the sleeve and barrel. In-other words, the distances between the two shoulders governs :themovement required before engage- 'ment. For varying the distance between the two ="shouldersfit is only necessary to-turn the sleeves 90 and -0l relatively which will adjust the positionof'theshoulder 01 on sleeve 9| with respect 'turnablein'rorder to make'thisna'djustment, it is also expedient that turning not accidentallyocvcure and in order tonormally prevent turning of sleeve-=9! on the sleeve--90; af-plunger "I 20 is provided as shown by Figs." Z'a-nd 3. m'I'his-p'lunger is 'disposedin arecess let in the end wall I05 of sleeve 90 and is pressed outwardly by means of -aspring 4-22. .The outer end.:of the plungeriis adaptedto selectively fit ciroumf'erentially spaced notches l23z axrra-nged" on the innerperiphery of the end -o-fsleevex Sit-and theouter endof the-sleeveoverhangs 'the--plunger"l20 .so-"that turned on the-sleeve 90 until the sleeves. are in the-positions.desired, and then fthe plunger may -be allowedto enteran adjacent notch 123.

=-will be apparent, ofcourse; that the plnsw93on :the -rbarrel 6 9i prevent iturningnof- :the f sleeve SEl relatively to-the "barrel.

T Fluid --under pressure wmay fw'be "conducted through'the lines [9 and -44 to either side'fofithe 4, piston (i 3 and ordinarily high :fluiol" pressureswill be required at the-left side :tof the" pistontsince at one side -of-"the pist0n while beingallowed to flow into :t-he icylinderat :the .;opposite:s idei=:ofi the "piston.

: Assuming 'thatther'dimpling: 'operationtis now to beperformedpthev die 19'with attached pin is associated with theasheets TI and l8aandl-xthe mandrelis passed through a' previously drilled .opening. inthe sheetsiaroundwhich the dimpling .-is tovoccur. Theidimpling mechanism is moved '=overthe'projectingmandrel to the position shown 1-75 "in Figal'and it rwilr now. be readily apparent-that when the mechanism is moved over the projecting end of the mandrel, the guiding devices III will facilitate movement of the mandrel into the end of the tool I2,

When the parts are positioned as shown in Fig. 1, and the rubber bushing is against the sheet 18, the operator applies further pushing effort to the mechanism and toward the sheet I8 and this will cause the barrel 69 and tool I2 carried thereby to move to the left relative to the sleeves 96 and BI, and, as a result, the tool I2 will spread the guiding devices III and move through the end wall I and through the rubber bushing. During this action. the spring 95 is compressed and the shoulders 91 and IM relatively approach each other. Final movement of the plunger '52 manually in this respect, causes the grooved end of the mandrel to move into the space between the jaws 54 until it engages the end of the reduced portion 58 of the plunger 59. i This serves not ce to the operator that the parts are in operative position and in particular that the end of the mandrel is located properly between the jaws.

When the parts are in this relation, the fluid under pressure is caused to enter the cylinder at the left side of the piston I3 and to exhaust from the right side of the piston and as a result the piston I3 will move to the right relative to the cylinder. The first part of this movement will cause the jaw holder 5| to move relative to the jaws 54 and clam ing of the jaws about the end of the mandrel will occur. Further movement of the jaw holder and piston. then will carry the jaws and mandrel therewith but if the sheets I? and I8 are in relatively fixed position, the piston and parts carried thereby instead of moving, will remain stationary so to speak, while the barrel will move to the left. In any event, after the piston has moved sufficiently to cause the jaws to be clamped abrut the end of the mandrel, relative axial movement of the barrel and tool 12 with respect to the mandrel will occur and this will cause the frusto-conical end of the tool to move through the bushing and to press the sheets 11 and 18 into the die recess 80 thus performing the dimpling operation. During the dimpling operation, the shoulders I65 and 91 on the barrel 69 and sleeve 9|, respectively, will engage each other and then the sleeves 90 and ill will be directly and positively moved by the barrel and will forcefully press the rubber bushing to apply the pressure against the sheet I8. Thus, this pressure becomes positive and direct except for the resiliency of the rubber during the dimpling operation, although the pressure may become positive and direct earlier or only during part of the dimpling operation, depending upon the location of the shoulders 91 and I023 relatively. From this it can be seen that the shoulders 97 and Iiiil can be adjusted axially in a relative sense so that the barrel will pick up the sleeves 0 and l at a desired time to cause direct and positive pressure through the rubber bushing and against the sheets El and I8. While preliminary movement of thebarrel relative to sleeve 9I will compress the spring Q5, ordinarily this pressure would not be of such character as to bend the sheets as the spring ordinarily is used to return the sleeves 9i! and 9! to their lefthand position when the parts return to inoperative positions as seen in Fig. 1. By placing the shoulders 97 and It!!! closer together, positive and direct pressure to the rubber bushing can be secured earlier and it follows that the pressure applied by the rubber will become greater and greater as the tool and die move tog-ether. The amount of pressure thus can be determined by adjustment of the shoulders 91 and IE0 relatively, and as stated before, modification of the bending of the sheets during the dimpling operation can be varied and the contour of the sheets can actually be governed as may be found most desirable.

Fig. 4 shows the parts on a larger scale approximately at the end of the dimpling operation. Deformation of the rubber naturally will occur owing to its incompressible character and accordingly it will expand as shown.

In effecting the aforesaid dimpling operation, a fluid pressure system may be employed as diagrammatically illustrated in Fig. 1 and which generally may correspond to the system embodied in my Patents Nos. 2,088,859 and 2,132,112. This system includes a fluid tank or reservoir I24, a motor driven pump I25, a control valve I25, solenoids I21 and I28 for moving the valves in opposite directions, respectively, and a pressure booster I29 including a small barrel NH. The supply line leading from the pump is indicated at I32 and an adjustable relief by-pass valve I33 in this line is also connected to a return line I34 leading to the tank. The valve allows the liquid to by-pass to the tank when necessary and may be so adjusted that the necessary dimpling pressures in any case will be available before bypassing occurs. Fluid is delivered to the booster when the valve I25 is in one position and from the booster barrel I3I, the fluid flows through a line I35 leading to the valve I26. With the valve H6 in one axial position, fluid is supplied toline I9 directly from the pump in order to return the piston I 3 to its inoperative position, whereas, when the valve is reversed, the line 44 is placed in communication with the barrel I3I. Higher pressure is available therefore for the working stroke but when this pressure reaches a definite amount, the valve I33 will all-ow by-passing from which it follows a definite but adjustably limited pressure may be employed for governing the character of the dimpling action.

A trigger I30 on the handle II may control switches not shown for either energizing one or the other of the solenoids I27 and I28 depending upon whether the trigger is moved in one direction or the other.

From the foregoing it will be understood that when the trigger is operated to eifect the dimpling operation, the tool I2 will press the sheets into the die recess until the edge of sheet 'II strikes the bottom 88 of the die and then continued movement of the tool will deepen the dimple since the metal is unsupported between the bottom 88 and. shoulder 8I of the die, but the resistance to dimpling increases with the dimpling, and as flattening of the edge occurs and at a predetermined pressure, the valve I33 will operate to by-pass the liquid to the tank. It should be appreciated that a high pressure is not required to dimple the metal and to get the correctdimple angle since the die'is unsupporting to the side of the dimple, while at the same time it should be appreciated that cracking is prevented by the flattening and upsetting of the edge of the sheet metal.

Under certain circumstances, liquid-under pressure may be supplied to the line 44 and air under pressure to the line I9 in accordance with the supply system disclosed in my Patent No. 2,053,- 718, relating to Riveting mechanism. In this case, the trigger I30 will operate a valve on the handle for connecting and disconnecting the pass i e 18*and-line I9t0 eXhaustor atmosphere and operation of the trigger -in this way as disclosed in sucnpatent will cause-the required movements of' the piston.

Upon-completion of the dimpling operation;- release of--the trigger l3il causes the linewd l to bee come open to return or exhaust-while the line.

I9 is open to fluid pressure. Then the piston-I3 returns to its-lefthandposition-and finally' the jaws 54 -strike the-right end of the-tool 12 and expandso that themandrel-is released. Then the mechanism can be bodily moved away from the meta1 sheets following which the par-ts may 'be associated-With another-opening in ordersto. effect thepatent will correspond to the-trigger I3il in the present application so-that operation otthe trlgger-l3il will control the-system in the man? here-that theswitch inthe patent controls thes supplying of fluid under pressure in the i lines I 5 f and+l6. In usinga system of this character,-op-

eration of the'switch will cause flu'id under-pres suretobe supplied to line- 44 until resistance-ist encountered suchas when the end ofsthe tool-'12 first engages the pIate 'IB andthen a highervfluid pressure may automatically be supplied to perform the dimpling operation, In this system,.. when "the *pressure'on the piston; reaches a prede termined-amountinthe dimpling operation, automatic reversal of fluidfiow may o'ccur'so-that'th'e piston-will be reversed automatically. I

all the systems,- it is desired that the control be simple and handy for the operator, suchas-by employing a trigger -onthe handle of the-gun andthat the;lines-.-l9 andbe fiexiblein-char actergso thatthe fiuid supplying :or: developing-,= source can be located remotely to -the: dimplin'g mechanism-fromwhich it follows'that the operator may be atgsome distance--from -thesourceaof fluid pressure while still "maintaining complete l control through a :simple form of "controlling:- It" might-be' added I that Where the triggeron the handle operates electrical controlling means; wires will lead..frommeans on the mechanisms thehandle to the electrically controlled valves or means at the source I of pressure-development In the construction shownby-Fig'uresfigifi, -andi 7,' a different means'for applying -pressure'to the sheets is=provided-,= and-principally the difference resides-intheuse of-fluid pressure-means at-th'eend-ofthe-casingz In this-case, a barrel M0115 used which takes the-pla'ceof the barrel -.69;and

inner -end of th'e barrel; is thre'adedrion the flange fil of the 'bushing 231 The tool indicated at I4 I is threaded-into theend wall of "the barrel 1 I 20, and has anannular, channelwlikermembem I 42 threaded thereonas. indicated at; I 43 so that I the member, barrel-and to'ol-moveas a unit.- The;

channel in the member I42 which is indicated at-I l I fo'rms acylindricalaspace fora-ring-like: piston I 45 i thatis adapted to: beamoved axially I by-fiu'id pressure through a line-I 4ezcommunicat-: ing with the channel-space atthe right side-eitherpisto'n =14 5 and (which leads to the space: at :the left 1 side =of the piston- I 3:? A pressure reducing valve :I 47 may- :beprovided in the line I 46 so "that; the pressure supplies: to the. space I44 maybe varied or regulated as desired; Thisiyalve may' soafunctio'n :th'atpressureusupplied ito, the; space; Mtmay beconstant' or a valvemaybezused'whig i causes the ressuresupplied to the space -I to be proportional to the pressure supplied-to -the=-- left side of the piston' I 3:

The ring-type piston I45 terminatesat its left" end in a threaded-mange: I45a which. is threadedly connectedto a threaded fla'nge- I 48 extending axially from a ring-plate I49. Sealing rings; and I5I- are-providedat the radially inner and. outer-sides of-the space 1 Mlfot engagement'with thepiston-I IS ih order-to prevent fluid from leak! A lngaxially past the piston and. thesezrings'are respectively' held in position by-means of threaded bush-in'gs- I 52 and. :I 53': threaded .ontthe inner andouten-legs-of th'echannel m-emberzl lz. The bushing I 53:? has -anlinwardly-offset portion I55.- which is:so arranged thatmovement of the pis- 1 ton M5 'is definitely limited inpordertowmaintain the parts assembled; Th'e plate-I491carries a rubber-bu-shingdil 'andsthis. bushing :may be on the ordersof-thatpreviously describedin con-- nection-:Witl1'jFigure- 1.": No means-.for-centeringy the'endo'f'the mandrel 84iwlthrespecttothe bore in the tool-J-Mjsls provided inr.this-case; but :itlis evident that if foundgxbedienh; a centeringdervice :such: as employed -,in Figure --1 couldalso: be-i employed in the second-structures; This could he L readilya accomplished byremploying a ring plate 1 I file-which 'is thicker insa direction-axially of-;the mechanism;'pro.viding radially gnovable "centering land guidingtdevices; such as 'are providedin'the end lwall' I 05in :the str11ctur ershoWn--,by-Figure-1 andproviding.fongreaterrelative axial movement I In ioperatingzthe, structure:shown: in Figs; 5; 6 and.7, themechanismzis movedgover the mandrel; 84j untilthe grooved end of the; latter -is -clisposed'betvveenthe jaws and upongintroduction fluid under pressure to the left :siderof ,the piston I 3," the jaw holder. is first moved I to;.. clamp the jaws-' about, the end of thewmandrel :and then movement of the jaw holder,- piston and mandrelrelative to-the barrel l 411 occurs. Itffollows that the tool I4 I and -the-mandrel 84 andw'die .19willhave relativemovement-axiallyof the mechanism and that the plates will" be-dim-pled by the end-oi the toolipr essing, the sheet into the die recess.- By-employing fluid-pressureforforcing therubber bushing I60 against the-plate, a variable pressure may be obtained to secure the results desired and this pressure may be variably; proportional to the fluid pressureemployed in the dim-pling operation or it may, be a constant, but adjustable pressure ependin'ellnon .t exr su a emean s de pressure regn atin eme ns.lusedflmav e 015 a "conv nti nal type. Wel know i the rt- Fignre ,7 shovvsihe .dimpled. sheets following o eration ,of the mec nism .shown by. Fi ures 5 and 6, andlshows .the, resilient bushingh as compressed, lt should be, understoodsthat, when the operation is reversed by;i admitting. fluid to, the right zot the piston ,and exhausting it frorn the 1eft; .th.e mm able pa ts w l .reversely mo and finally: hat-the jaws.v will r le sed so, that. the mandrel may be .separat di om. the mec an m.

N 0w ref-strin to Figs, 8 to NiQ usiVefl h m henismediscl ed dnit e e-fi ure a enerally similar to that; shown by Fie, wit t e principal exception-that; an ar vil is movable with the tool 12' and; is;adapted .to;-engage;the sheet, metal. In this: structure, ;a sle ve I60 issubstituted forth,e;s1eeve.'-99;shownsi igs 1, but the two sleeves are; threadedly connected in the same manner;

and cooperate with; the zb rrelfiiandtparts car-1 izes the corresponding parts in Fig. 1. For guiding the mandrel 84 into the end of the tool 12, a guiding and centering device I6I is employed, which is on the order of that provided in Fig. 1, excepting that in this case it is slidably movable with respect to the sleeve I60, instead of being arranged in. an end wall of such sleeve. The guiding and centering device I6I is in the form of a ring which has a close but sliding fit with the inner periphery of the sleeve I60, as indicated at I62, and the inner periphery of the ring slides on the outer surface of the tool 12. Also, the guiding and centering device has a tubular portion I64 at its outer side and the dimensions of this portion are sufficiently large to permit the tool 12 to move therethrough. A pad I65 comprising a ring of resilient material such as rubber, surrounds the tubular portion I64 and is maintained thereon at the outer end by means of aradial flange or shoulder I66. At its axially inner end, the rubber ring contacts a radial flange i61 on the outer end of the sleeve I60 and the character of the rubber ring is such that normally it tends to move the centering and guiding device I El relative to the flange I61, so as to maintain the ring part of the centering device against the inner side of the flange. It may be observed that with the parts in initial positions, as shown in Fig. 8, the guiding and centering portions III are disposed substantially in contact with the conical end 81 of the tool 12, from which it follows that the centering portions are in position to guide the end of the mandrel into the end of the tool.

Now directing attention to enlarged views I and I I in particular, it will be noted that the outer end of the tubular portion I64 terminates slightly beyond the radial flange I66 in an anvil I10, which is adapted to engage the sheet metal immediately around the area being dimpled. The anvil end face diverges outwardly with respect to the sheets as seen in Fig. at an angle of 10, for instance,

and this angle is selected so that if the anvil coins the metal under said face, the angle which the coined surface makes with the sheet surface will be the same or slightly greater than the corresponding angle of the fairing on the rivet embodied in an application for patent filed herewith and to which further reference is made hereafter.

With respect to operation of this mechanism, several generalities may now be stated. In the first place, it is desired prior to insertion of the mandrel that the guiding and centering means be in proper position, as shown by Fig. 8. in

which case the ring part of the device will be in contact with the flange I61 on the sleeve I60. It is also desired that the rubber pad be pressed against the sheets at least prior to the completion of the dimpling operation, so as to counteract and neutralize the tendency in the sheets to bend on account of the dimpling action. It is also desired that the flange 13 on the tool 12 engage the inner side of the guiding and centering device IGI so as to pick up the latter and cause it to move with the tool when the dimple has been formed to the proper depth.

Assuming that the mandrel and die are in positions as shown in Fig. 8, the operator moves the handle and barrel 69 carrying the tool I2 relative to the sheets and die so as to cause the tool '52 to move through the guiding and centering device IBI until the inner end of the mandrel meets the stop previously described in connection with Fig. 1, at which time the outer end of the 14 tool substantially contacts the sheet metal. At this time, the shoulder I00 on the barrel 69 preferably is slightly spaced from the shoulder 91 on the sleeve 9|, depending upon adjustment of the sleeve 9I with respect to the sleeve I60. It

will be understood in this connection that by turning the sleeve 9| relative to the sleeve I60, the shoulders 91 and I00 may be moved toward and from each other so as to govern the time when they contact and hence the time when the rubber will be pressed against the sheet metal and the amount of pressure applied.

With the parts as shown in Fig. 9, the operator presses the trigger I30 to cause the mechanism to function and when this occurs the mandrel and tool have relative movement which causes the conical end of the tool to press the sheet metal into the cavity in the die. When this occurs, the metal is dimpled into the die cavity and the corner edge of the inner sheet 11 becomes flattened against the base of the die cavity. At the time the dimple has the formation desired, the flange 13 on the tool contacts the inner wall of the guiding and centering device I6I so that further pressure acts through the anvil I10 as well as the tool 12 and this contact serves as a means for stopping or limiting further relative movement of the tool and die. It is intended that the pressure operating in the working stroke of the mechanism be so limited by the by-pass valve I33 or otherwise depending upon the particular system employed, that in the case of the thickest sheets of metal to be dimpled, the dimpling operation will require a little less than the maximum pressure available so that only a small differential of pressure will be taken through the anvil I10. In other words, in the case of the thickest sheets, when the anvil contacts the sheets upon formation of the dimple. only a small amount of additional pressure will be required to cause the by-pass valve I33 to function. This additional pressure may cause slight coining of the metal under the anvil, so that a shallow recess will be formed, but any movement of the anvil and tool therewith, by such additional pressure, will not undesirably change or alter the dimple. When thinner sheets are being dimpled, with the same pressure limitation as in the case of the thicker sheets, the pressure required for dimpling is much less and resistance to movement of the tool is less and therefore the anvil takes a greater amount of the pressure before the valve I33 by-passes, and deeper coining of the metal under the anvil will occur.

From the foregoing, it should be understood that the operator may use the mechanism for dimpling sheets of diiferent thicknesses without varying the adjustment of the valve I33 or making any other adjustments on the mechanism. Hence, the dimples may be formed without regard to changes in the thickness that may occur in an airplane cover, for example, with the assurance that a proper dimple will be formed in each instance.

It might be added here that if a system is used such as disclosed in Peterson Patent No. 2,163,627, the mechanism would reverse just as soon as the pressure reached the limiting amount.

bezadlusted so;.that1the contour of. the-.sheetswill. rema-imfiatpor normal", aftergdimpling operations are completedron the:sheets,:althoughithe,sheets may; bei'cha-ngedto. a convexror. concave contour depending upon the pressure-applied by theruba bet, and thisspressureds determined by the aol-. ju'stmentof the; relative positionsofshoulders'97: an'drltfl on-sleev.es 9i: and barrel 69:, respectively;

The sdimplerthus-formed in the'sheets'rhas a conical portion: H" corresponding towthe :conical taperzon :the end oithe: tool l2 and at'the outer edge of the dimpleythemetal may bezcoined more or. lessrandfia .rshallow recess corresponding in angul'arityto the angle of theanvil'llfl isvformed, as indicated at l l5; Betweenithetshallow. recess and: isoutof contact witlrthe conical surface of the tool. This: particular :dimpling action adapts thexdimpled recess toza particular-rivethaving. av

fairing. for covering the shallow recess [16, if any, and'..for.;covering. thecurved part of the dimple, and .aiconical .portion adapted .to fitthe, conical portionzl l5 blithemecesszs. A/separate' application is being filed on a rivettsuch as mentioned, and this application forzpatent isidentified as Serial No.-.352'205;ifi1ed. August 12;:1940, now PatentNo.

Aslsta'ted heretoforegtheplates'l'l' and 18 may comprise laminations of an airplane cover and in this event they may. be constructed of an aluminum alloy; It will'beunderstood pursuant to this thatthe die. 19; tool 72'; pin 84;-anvil I; and other parts willbeformed :of suitably hard metal to perform the functions necessary in the use of themechanism':

It will be apparent. that all of the operations insofar as the use of force is involved occur at only one side of the sheets and that no backing element requiring forceful manual'holding at the" oppositeside-of the sheet is required." In other words itiis-onlynecessary for the operator to: insert-the mandrel at one side of the sheet and move the die' 19 thereoninto position and thenitis a simple matter to hold them in that positionwhile the mechanism is moved over the mandrel at the other side of the sheet. It may beadded here that after the dimpling operation, the opening through the: sheets may be enlarged slightly by a drill for example; to provide a more fully'cylindrical and smooth hole, as disclosed in mycopending application, Serial No. 327,138, now

Patent: No; 2,292,446.

If the dimpling point is substantiallyremoved from the edges of the sheet, a handle may be employed for allowing the operator to insert the mandrel at a point substantially removed from the edge. A handle I70 is shown on the die for this purpose, although it is to be understood that the handle may be releasable so that it could be connected to the die only when needed. In any event, the handle allows the operator to place the mandrel and die in position even though the opening in the plate is substantially removed from the operator and relatively inaccessible'and thus access to difierent points interiorly of an airplane cover, for example, may easily be had.

Since it is only necessary-to insert the mandrel throu h-the opening-in; the plate; and lightly hold the mandrel in place while the mechanism is pushed over the end of the latter, it can be easily seenthat an operator will have no difficulty in 3 l 'i'fi'sand the. conical: portion l l 5;:the sheet: metal: remains curved asra result-of the bending action.

anism, allzthe operatorneeds to do isto pull. the:-

mandrelaway'from-the sheets of metal.

Dimpling .-can be-rapidly' performed in this-- manner .even 'atpoin't-s inaccessible and all dim pling; operations can beperformed while the sheets are in place on airplane wings or fuselages--. or other-installationswhere sheets may be dim-- plednfor-subsequent riveting. Aside from this, thermechanism' can :be adjusted so that bending ofrthe sheets that'ordinarily would occur as a resultof dimpling can be neutralized or counteracted. so that finaliy'undesirable deformations or ben'dsican be avoided in the sheets. By having thermec-hanismconnected to a remote source of fiuidiunder pressure; the operator can quickly move-=from point to point for effecting one dim pling. operation after another and since the gun is i-compact and light, this procedure is not fa-.

tiguing. Moreover, since the entire operation can" .bGl-CODEIOHECI by means of a trigger on the handle,

all-that-theoperator needs todo is .to moveth'e r gun from one place to another and push it over the-mandrel-or-mandrels successively and repeatedly move thetrigger-for efiecting the dimpling operations.. Two operators, one handling the mandrel-and die device and moving it from point to point, and the other operating the dimpling mechanism and moving it from point to point,

thus rcan -.rapidly reffe'ct one dimpling operation after another while the sheets are in place on the structure. Rapidity of dimpling of airplane structures. is thus increased and the dimpling casing, pin'gripping means carried by the fluid pressure responsive means, a tool movable with the casing and having a central bore extending axiallyi'of the casing and having an end adapted towpressthe metal sheets at one side, a die elementiadapted to be disposed at the opposite side of the sheets and having a pin adaptedto-pass through-the opening in the latter and through the bore inthe tool and to be gripped by the pin grippingmeans, whereby upon actuation of the fluid pressureresponsive means, the tool and die may be moved towards each other to dimple the metal, means. on the casing adapted to apply pressure to the sheets around the dimpling area in OIdBl1l3O modify bendingof the sheets during the dimpling operatiomiand means for varying the pressure --applied to: thev sheets by'the last men tionedsmeans. during. a predetermined amount of dimpling.

2. Aniap-paratus forrforming a dimple around an opening in metal sheets comprising a casing; -movable fluid pressureresponsive means in thecasing,v pin gripping:meansicarried.by the fluid pressure responsive meansya tool movable with the casing and :having a central bore extending axially of the casing and having an end adapted to; press the metal sheets at one side,'a die elementadaptedto :bedisposed at theopposite side of. theusheetsgand'having a pin adapted to pass throughxthez opening in-therlatter and through ther-boreain thei'itoolxand to ibegripped by the pin grippingmeansywhereby upon actuation of the fluid pressure responsive means, the tool and die may be moved towards each other to dimple the metal, resilient means on the casing adapted to apply pressure to the sheets around the dimpling area in order to modify bending of the sheets during the dimpling operation, and means for varying the pressure applied by the resilient means during a predetermined amount of dimpling.

3. An apparatus for forming a dimple around an opening in metal sheets comprising a casing, movable fluid pressure responsive means in the casing, pin gripping means carried by the fluid pressure responsive means, a tool movable with the casing and having a central bore extending axially of the casing and having an end adapted to press the metal sheets at one side, a die element adapted to be disposed at the opposite side of the sheets and having a pin adapted to pass through the opening in the latter and through the bore in the tool and to be gripped by the pin gripping means, whereby upon actuation of the fluid pressure responsive means, the tool and die may be moved towards each other to dimple the metal, a sleeve axially slidable on the casing and being telescopically related to the tool, means on that end of the sleeve adjacent the metal pressing end of the tool adapted to apply pressure to the sheets around the dimpling area in order to modify bending of the sheets by the dimpling operation, and means for urging the sleeve along the casing in a direction to apply such pressure to the sheets around the dimpling area.

4. An apparatus for forming a dimple around an opening in metal sheets comprising a casing, movable fluid pressure responsive means in the casing, pin gripping means carried by the fluid pressure responsive means, a tool movable with the casing and having a central bore extending axially of the casing and having an end adapted to press the metal sheets at one side, a die element adapted to be disposed at the opposite side of the sheets and having a pin adapted to pass through the opening in the latter and through the bore in the tool and to be gripped by the pin gripping means, whereby upon actuation of the fluid pres- I sure responsive means, the tool and die may be moved towards each other to dimple the metal, a sleeve axially slidable on the casing and being telescopically related to the tool, means on the end of the sleeve adjacent the metal pressing end of the tool adapted to apply pressure to the sheets around the dimpling area in order to modify bending of the sheets by the dimpling operation, and abutments on the sleeve and casing adapted to engage each other upon predetermined movement of the sleeve and easing relatively whereby the sleeve will be directly moved by the casing through engagement of the abutments after a predetermined movement of the casing relative to the metal sheets during the dimpling operation.

5. An apparatus for forming a dimple around an opening in metal sheets comprising a casing, pin gripping means movable in the casing, a tool movable with the casing and having a central bore extending axially of the casing and having an end adapted to press the metal sheets at one side, a die element adapted to be disposed at the opposite side of the sheets and having a pin adapted to pass through the opening in the latter and through the bore in the tool and to be gripped by the pin gripping means, means for moving the casing and pin gripping means relatively whereby the tool and die may be moved towards each other to dimple the metal, means on the casing adapted to apply pressure to the sheets around the dimpling area in order to modify bending of the sheets during the dimpling operation, and means for varying the pressure applied to the sheets by the last mentioned means during a predetermined amount of dimpling.

6. An apparatus for forming a dimple around an open ng in metal sheets comprising a casing, pin gripping means movable in the casing, a tool movable with the casing and having a central bore extending axially of the casing and having an end adapted to press the metal sheets at one side, a die element adapted to be disposed at the opposite side of the sheets and having a pin adapted to pass through the bore in the tool and to be gripped by the pin gripping means, means for moving the casing and pin gripping means relatively whereby the tool and die may be moved towards each other to dimple the metal, a sleeve axially slidable on the casing and being telescopically related to the tool, means on that end of the sleeve adjacent the metal pressing end of the tool adapted to apply pressure to the sheets around the dimpling area in order to modify bending of the sheets by the dimpling operation, and spring means for urging the sleeve along the casing in a direction to apply such pressure to the sheets around the dimpling area.

7. An apparatus for forming a dimple around an opening in metal sheets comprising a casing, pin gripping means movable in the casing, a tool movable with the casing and having a central bore extending axially of the casing and having an end adapted to press the metal sheets at one side, a die element adapted to be disposed at the opposite side of the sheets and having a pin adapted to pass through the bore in the tool and to be gripped by the pin gripping means, means for moving the casing and pin gripping means relatively whereby the tool and die may be moved towards each other to dimple the metal, a sleeve axially slidable on the casing and being telescopically related to the tool, means on the end of the sleeve adjacent the metal pressing end of the tool adapted to apply pressure to the sheets around the dimpling area in order to modify bending of the sheets by the dimpling operation, spring means for urging the sleeve along the casing in a direction to apply such pressure to the sheets around the dimpling area, and abutments on the sleeve and easing adapted to engage each other upon predetermined movement of the sleeve and casing relatively whereby the sleeve will be directly moved by the casing through engagement of the abutments after a predetermined movement ofthe casing relative to the metal sheets during the dimpling operation.

8. An apparatus for forming a dimple around an opening in metal sheets comprising a casing, pin gripping means movable in the casing, a metal pressing element movable with the casing and having a bore extending axially of the casing and having an end adapted to press the metal at one side, a second metal pressing element cooperable with the first and adapted to press the metal at the other side and having a pin adapted to extend through said bore and to be gripped by the pin gripping means, means for moving the pin gripping means and easing relatively whereby the two pressing elements may be moved towards each other to dimple the metal, means movable with the casing for applying pressure to the sheets around the dimpling area in order to modify bending of the sheets by the dimpling operation, and means for varying the operative position of the last mentioned means in order to vary the pressure thereof during the dimpling operation.

9. An apparatus for forming a dimple around an opening in metal sheets comprising a casing, pin gripping means movable in the casing, a metal pressing element movable with the casing and having a bore extending'axially of the casing and having an end adapted to press the metal at one side, a second metal pressing element cooperable with the first and adapted to press the metal at the'other side and having a pin adapted toextend through said bore and to be gripped by the pin gripping means, means for moving the pin gripping means and easing relatively whereby the two pressing elements may be moved toward each other to dimple the metal, means movable with respect to the casing for applying pressure to the sheets around the dimpling area in order to modify bending of the sheets by the dimpling operation, and abutments operatively carried by the casing and movable means and adapted to engage each other upon predetermined relative movement of the casing and pin gripping means during'the dimpling operation.

v10. .An apparatus for forminga dimple around an opening in :metal sheets comprising a tubular "casing, pin gripping means axially movable in the casing, a tool projecting from one end of the casing and terminating in a frusto-conically shaped end adapted to press the sheets at one side, said tool having a central bore and being aligned with the pin gripping means so that a pin may be pushed through the tool and engaged by the pin gripping means, a die member to bondsp'ose'd at'the other side 'of the sheets and having pin adapted .to project through said opening in the latter and "through 'said bore for engagement with said gripping means, means for relatively moving the gripping means and tool axially of the casing so as to bring the tool and die into sheet dimpling positions and for returning the gripping means and tool to inoperative positions, and iretra'ctible guide means adjacent the frusto conical end of the tool and operative to guide the end of the pin into the bore when the tool is in inoperative position and being retractible so that during the dimpling operation the tool maymove into contact with the sheets.

11. An apparatus for forming a dimple around an opening in metal sheets comprising a tubular casing, pin gripping means axially movable in the casing, a tool projecting from one end of the casing and terminating in a frusto-conically shaped end adapted to press the sheets at one side, said tool having a central bore and being aligned with the pin gripping means so that a pin may be pushed through the tool and engaged by the pin gripping means, a die member to be disposed at the othersideof the sheets and having a pin'adapted .to project through said opening in the latter and through said bore for engagement with said gripping means, :means for relatively moving the gripping means and tool axially of the casing so as to bring the "tool and die into sheet dimpling positions and for returning the "gripping means and tool :to inoperative positions, and radially movable guide elements carried by the casing adjacent the 'frusto-c-onical end of the tool for guiding the pin into the bore and adapted to be outwardly moved by the tool during initial movement of the latter in the dimpling operation so that the elements will not interfere with contacting 0f the tool with the sheet metal.

v 12. An apparatus for forming a dimple around an opening in metal sheets comprising a tubular casing, pingripping means axially movable in the casing, a tool projecting from one end of the-casing and terminating'in a frusto-conically shaped end adapted to press the sheets at one side, said tool having a eentralibore and being aligned with the pin gripping means so that a pin may be pushed through the 'tool and engaged by the pin gripping means, a 'die member 'to be disposed at the other side of the sheets and having a pin adapted to project through said opening in the latter and through said bore for engagement with said gripping means, means for relatively moving the gripping means and tool axially of the casing 50 as to bring the tool and die into sheet dimpling positions and for returning the gripping means and tool to inoperative positions, movable guide means carried by the casing adjacent the frustoconical end ofthe tool for guiding the pin into the bore and adapted to be outwardly moved b the tool during initial movement of the latter in the dimpling operation, and spring means for returning the guide means to operative position when the tool and pin gripping means are returned'to inoperative position.

13. An apparatus for forming a dimple around an opening in metal sheets comprising a tubular casing, pin gripping means axially movable in the casing, a tool projecting from one end of the casing and terminating in a frusto-conically shaped end adapted to press the sheets at one side, said tool having a central bore and being aligned with the pin gripping means so that a pin may be pushed through the tool and engaged by the pin gripping means, a die member to be disposed at the other side of the sheets and having a pin adapted to project through said opening in the latter and through said bore for engagement with said gripping means. means for relatively moving the gripping means and tool axially of the casing so as to bring the tool and die into sheet dimpling positions and for returning the gripping means and tool to inoperative positions, an axially movable member on the casing and extending along the tool, and means on the end of the said axially movable member adapted to contact the sheet metal around the dimpling area in order to modify bending oi the sheets during the dimpling operation said last mentioned means comprising a resilient rubber bushing and a relatively hard, annular confining element for preventing the rubber from flowing radially inwardly when it is pressed against the sheet metal while still allowing the tool to move relative to said member.

14. An apparatus for forming a dimple or the hire in metal sheets comprising a die member and a tool member adapted -to be disposed at opposite sides of the sheets and to be moved axially towards each other to engage the sheet metal, a rubber bushing around one of the members and adapted to press against the sheet metal around the member, and an annular confining element on the bushing adapted to prevent the rubber from flowing inwardly towards the member at thatend of the bushingadapted to contact thesheet metal.

15. An apparatus for pressing metal sheets comprising members adapted to be disposed at opposite sides of the sheets respectively an'dto be moved axially towards each other to engage the sheets, fluid pressure operated means 'for relatively moving the members to'sheet'engagingpositions, means axially movable on one member for applying pressure to the metal around the area operated on by the members in order to modify deformation of the sheets by the action of said members, and fluid pressure means for moving 21 said axially movable means relative to the member upon which it is movable.

16. An apparatus for pressing metal sheets comprising members adapted to be disposed at opposite sides of the sheets respectively and to be moved axially towards each other to engage the sheets, fluid pressure operated means for relatively moving the members to sheet engaging positions, means axially movable on one member for applying pressure to the metal around the area operated on by the members in order to modify deformation of the sheets by the action of said members, a second fluid pressure operated means for moving said axially movable means relative to the member upon which it is mounted, means interconnecting the tWo fluid pressure means so that the fluid is operable on both means, and means effecting a differential in the fluid pressure operable against the second fluid pressure means.

17. An apparatus for forming a frusto-conical type of dimple around an opening in sheet metal sheets comprising a die element adapted to be disposed at one side of the sheets and into which the metal is pressed during the dimpling operation, a tool element having an end adapted to press the metal into the die element, abutment means movable with the tool and engageable with the sheet metal around the area to be dimpled for positively limiting movement of the tool into the die opening, and resilient means movable against the sheet metal around the abutment means for controlling the tendency of the sheets to bend as a result of the dimpling operation.

18. An apparatus for forming a frusto-conical type of dimple around an opening in sheet metal sheets comprising a die element adapted to be disposed at one side of the sheets and into which the metal is pressed during the dimpling operation, a tool element having an end adapted to press the metal into the die element, abutment means movable with the tool and engageable with the sheet metal around the area to be dimpled for positively limiting movement of the tool into the die opening, resilient means movable against the sheet metal around the abutment means for controlling the tendency of the sheets to bend as a result of the dimpling operation, and fluid pressure means for moving the die and tool relatively to form the dimple and for pressing the resilient means against the sheet metal. 7

19. An apparatus for forming a frusto-conical type of dimple around an opening in sheet metal sheets comprising a die element adapted to be disposed at one side of the sheets and into which the metal is pressed during the dimpling operation, a tool element having an end adapted to press the metal into the die element, abutment means movable with the tool and engageable with the sheet metal around the area to be dimpled for positively limiting movement of the tool into the die opening, resilient means movable against the sheet metal around the abutment means for controlling the tendency of the sheets to bend as a result of the dimpling operation, fluid pressure means for moving the die and tool relatively to form the dimple and for pressing the resilient means against the sheet metal, and means for varying the pressure applied by the resilient means.

20. An apparatus for forming a frusto-conical type of dimple around an opening in sheet metal sheets comprising a die element adapted to be disposed at one side of the sheets and into which the metal is pressed during the dimpling operation,

a tool element having an end adapted-to press the metal into the die element, an anvil around and movable with the tool for engaging the sheet metal around the area to be dimpled, and means for moving the tool and die relatively to form the dimple, said anvil having an end face which makes an acute angle with the sheet metal surface around the dimple.

21. An apparatus for forming a dimple around an opening in metal sheets comprising a casing, movable fluid pressure responsive means in the casing, pin gripping means carried by the fluid pressure responsive means, a tool movable with the casing and having a central bore extending axially of the casing and having an end adapted to press the metal sheets at one side, a die ele-' ment adapted to be disposed at the opposite side of the sheets and having a pin adapted to pass through the opening in the latter and through the bore in the tool and to be gripped by the pin gripping means, whereby upon actuation of the fluid pressure responsive means, the tool and die may be moved towards each other to dimple the metal, an anvil around and movable with the tool for engaging the sheet metal to limit the dimpling operation, and means on the casing adapted to apply pressure to the sheets around the dimpling area in order to modify bending of the sheets during the dimpling operation.

22. An apparatus for forming a dimple around an opening in metal sheets comprising a tubular casing, pin gripping means axially movable in the casing, a tool projecting from one end of the casing and terminating in a frusto-conically shaped end adapted to press the sheets at one side, said tool having a central bore and being aligned with the pin gripping means so that a pin may be pushed through the tool and engaged by the pin gripping means, a die member to be disposed at the other side of the sheets and having a in adapted to project through said opening in the latter and through said bore for engagement with said gripping means, means for relatively moving the gripping means and tool axially of the casing so as to bring the tool and die into sheet dimpling positions and for returning the gripping means and tool to inoperative positions, retractible guide means adjacent the frusto-conical end of the tool and operative to guide the end of the pin into the bore when the tool is in inoperative position and being retractible so that during the dimpling operation the tool may move into contact with the sheets, an anvil around and movable with the tool for contacting the sheet metal around the dimpling area in order to limit movement of the tool into the die.

23. An apparatus for forming a dimple around an opening in metal sheets comprising a tubular casing, pin gripping means axially movable in the casing, a tool projecting from one end of the casing and terminating in a frusto-conically shaped end adapted to press the sheets at one side, said tool having a central bore and being aligned with the pin gripping means so that a pin may be pushed through the tool and engaged by the pin gripping means, a die member to be disposed at the other side of the sheets and having a pin adapted to project through said opening in the latter and through said bore for engagement with said gripping means, means for relatively moving the gripping means and tool axially of the casing so as to bring the tool and die into sheet dimpling positions and for returning the gripping means and tool to inoperative positions, retractible guide means adjacent :the trusto-conical :end .of :the tool and operative to guide the :end of the 'pin into .the bore when "the tool ..is in inoperative "position ;and :being metractible so that the tool may move past the i'ctractible means and into :contact with the sheets, an anvil onithe retractibleimeans adapted to engage the sheet metal around the .dimpling area to limit .the dimpling operation, and abutmentmeans .on'the'tool formoving the 'retractible means and anvil therewith after the retractib'le means ,ha's beenretracted :to allow'movement of the "tool past the rretractible means.

.24. :An apparatus 101' forming .a dimple around an opening :in metalrsheets comprising a tubular casing, pin gripping means axialy movable in the casing, "a .tool projecting from one end of the casing and terminating .in .a .frusto conicall-y shaped end adapted :to :press the sheets at one side, .said tool having a central bore and being aligned with the *pin gripping "means so that, .a pin may-be mushedthroug-h the tool and engaged vbyt'he ipin gripping means, a die member to be Iclisposedat the other side ofxthe'sheets and having .apiniadapted'to project through said opening in the latter and through said bore for engagement with said gripping means, means for relatively moving the :gripping means and tool axially of the casing soas to bring the tool and die vintocslh'eet :dimpling positions and :for returnmg the gripping means Land-tool to inoperative positions, .retraetible .aguide means adjacent the frus'to-conical end of the 'tool and operative'to guide the 'end of .the'pin .into "the how when the tool is in inoperative position and being retractible so that the ttool may move past the retractible means .and .into contact with the sheets, an anvil on athezretractible means adapted to engage the sheet metal around "the dimpling area to limit the dimpling operation, abutment means on the tool for moving the retractible means and'anvil therewith after the retractib'le means has been retracted to allow movement of thetoolipast the retractible means, and resilient means-around vthe anvil for 'pressingagainst the sheetmeta'lto modify bending of the sheetsduring the edimpling operation.

25. An apparatus for forming sheet "material comprising a support a tool member movable on thesupport and having a bore, :a second member cooperable with the tool in forming'the'material between them and having a pin passable into the bore of the .tool, means for relatively moving the tool andsecond member towardseach other to form the material between them, and retractible guide means carried by the support adjacent the end of the tool and operative to guide :theend of the pin into the end of the bore andzbeing retractible so that during the .forming operation the guide means is in an out of the way position.

26. ,An .apparatus .for forming sheet material comprising a support,'a tool member'movable'on the support and having a bore, asecond member coopera'ble with the tool in forming th'e'material between them "and having a pin passable .into the bore of the tool, means for relatively moving the tool and second member towards each other to form the material between them, retractible guide elements on the support adjacent ithe end of the tool for guiding the end of the pin into theend of the bore and being'retractible to an inoperative position, and means operable during movement of the'tool after the pin enters the bore for'retracting the elements so that they 'will not interfere with forming of the material.

LOUIS C. HUCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,292,446 Huck Aug. 11,1942 2,088,859 Huck Aug. 3, 1937 2,132,112 Huck Oct. 4, 1938 192,448 Morgan et a1 June '26, 1877 21,101,434 'I-Iatton June 23, 1914 1,873,451 McKnight et al. Aug. 23, 1932 1,173,471 Wilkinson Feb. 29, 1916 1,669,899 Coffer 'May'15, 1928 1,926,686 fNewton Sept. 12, 1933 72,127,969 -Dingwerth Aug. 23, 1938 

